Wot no brakes!

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Old-Guy
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Wot no brakes!

Post by Old-Guy »

The VSX has developed another, and rather alarming, trick: the first time the brake pedal is pressed after the VSX has been parked for some hours, nothing happens for a few seconds! I learnt long ago to WAIT until after the STOP light has gone out before moving, so it's not that. The longer the car has been left, the longer the delay. Today, after the car hadn't been used for 4 or 5 days, I nearly ended up in a neighbour's drive due to the 1-2 seconds delay!

If it were the Accumulator, from past experience I would expect the STOP light to take a long time to go out instead of the 10-15 seconds (depending on the amount of loading/unloading) that it actually takes. I'm worried that sooner or later, when I forget to give the pedal several firm presses before moving off, I'm going to hit something or somebody.

Anyone got any (sensible) ideas please?
2011 Grand C4 Picasso VTR+ 1.6HDi in Kyanos Blue
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - after 11 years now owned by XanTom
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
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Mandrake
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Re: Wot no brakes!

Post by Mandrake »

Hmm, that's very unusual indeed. No answers I'm afraid, but I do have questions.

Are you saying that even if you wait a good amount of time for the stop light to go out and the suspension to finish lifting there is simply no braking effort at all when you press the pedal for a couple of seconds ? Hard to see how that could happen because that would imply both front and rear brakes are not working.

What about the hand brake, I assume that is working ok or the car would have rolled away in the night ? (It's a manual and therefore without a park mode, right ?)

If the hand brake seems fine that would suggest that the front pads/discs and callipers are ok since the hand brake uses the same pistons as the foot brake... meaning that it's more likely a hydraulic issue.

Does the foot brake fail to work before the car begins moving - eg if you start the car, wait, apply the foot brake and release the hand brake at the same time does it start rolling away ? Or does the foot brake only fail to work when the car is already in motion at a few mph ?

If the latter try this - when you park the car for the night remove the under bonnet ABS fuse. You'll know you have the right one when the ABS warning light stays on while the engine is running. See if your brakes are still missing when first starting the next morning.

An ABS fault is one of the few things that can cause complete but temporary loss of all brakes, and it has been known to happen at very slow rolling speeds of a few mph due to faulty sensors, and without lighting the ABS fault light.

It's a very easy and relatively safe test to perform to rule out an ABS malfunction - remember low spec Xantia's don't come with ABS so you're no worse off than them during the test. If the ABS fuse removal makes no difference at least one thing has been ruled out.

Has this problem occurred suddenly or has it gradually crept up on you ? Have the brakes been bled since the symptoms appeared ? Is there any obvious frothing in the top of the hydraulic tank with the engine running ?
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
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Old-Guy
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Re: Wot no brakes!

Post by Old-Guy »

Thanks for your (sensible) thoughts Simon.

Hand-brake works fine; But, you set me thinking. New pads required for MoT when I bought it in June, old N/S/F outside pad incorrectly fitted - 'pip' sitting on edge of piston instead of inside cut-out so pad (and thus disc) worn wedge-shaped. Incurable squeal from brakes but with new pads it pulled dead square and passed the re-test.

The car is normally parked on a considerable slope (nose-up to avoid any risk of the wet boot problem), so I do a 'hill-start' to move off. I think that if I remember to try the brakes before I move off, I get rid of the problem. I do a hill-start on the sloping drive, pull forward slowly about 10m up the drive, dip the clutch as the front wheels go over the hump of the pavement and into the gutter, turn full lock left to drive forward some 30m to top of the hill at the end of the cul-de-sac, press the brakes (for the first time) and then frighten myself as nothing happens for a second or so! If I mis-judge the dip-the-clutch-at-the-hump and dab the brakes, the car heads for the hedge opposite (no pavement or verge on that side!)

Doesn't use any LHM ('new' car so all levels checked frequently. The brakes were thoroughly bled when I first had the car, but not since. The problem has crept up on me - the delay was barely noticeable, but it's getting dangerous now. On reflection, today the car had only been parked up for less than two days - left all Thursday afternoon in a public car park, remembered to wait after STOP went out, backed out of the space slowly and carefully, car rolled 2-3m after I hit the brakes before jerking to a halt (because I was ramming the pedal through the floor!).

In the morning (before the grass is dry enough to cut), I'll try pulling the ABS fuse and I'll check the reservoir for frothing - when I serviced the car on buying it, I cleaned the filthy LHM filters so I (very carefully) undid all the reservoir top connections and the pipes were all pretty hard. I did take care to push the pump feed pipe against the swell in the stub before snapping the clip tight, but .....
2011 Grand C4 Picasso VTR+ 1.6HDi in Kyanos Blue
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - after 11 years now owned by XanTom
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
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Clogzz
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Re: Wot no brakes!

Post by Clogzz »

nothing happens for a few seconds!
Had that, it was a flat rear accumulator; the anti-sink sphere.
2002 C5 2.0i AL4 230,000 km 76372389
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Mandrake
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Re: Wot no brakes!

Post by Mandrake »

Clogzz wrote:
nothing happens for a few seconds!
Had that, it was a flat rear accumulator; the anti-sink sphere.
That couldn't affect the front brakes.

Since the handbrake works fine my money is on either ABS or lots of air getting into the system through a split or leaking hose. This should show up as a frothy tank.
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
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Dommo
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Re: Wot no brakes!

Post by Dommo »

Does the brake pedal pulsate when it's not working? I find xantia abs to be quite easily upset by bumps, and when it does get upset you get no braking for around a second.
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CitroJim
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Re: Wot no brakes!

Post by CitroJim »

Guy, I've had the same problem and resolved it by replacement of both accumulators. It's hard to explain what's happening and it might well be ABS.

Another test is to pull the Hydractive fuse and see if it happens when the suspension is in forced hard mode...
Jim

Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...